1. Field of the Invention
The invention relates to a sealing device for laterally sealing at least one excess pressure or vacuum zone adjoining a moving surface in a paper machine having at least one sealing element that is arranged at least locally in a receptacle area of a holder and is movable relative to the holder for placement against the moving surface.
The invention also relates to a process for laterally sealing at least one excess pressure or vacuum zone adjoining a moving surface in a paper making machine by way of a sealing device that includes at least one sealing element that is arranged at least locally in a receptacle area of a holder and is moved relative to the holder for placement against the moving surface.
Such sealing devices and processes are used, for example, to seal off from the environment the interior, which is under negative pressure, of a suction box whose lateral walls are provided with the sealing device by pressing the sealing elements against the rotating jacket of a suction roll over which the paper web to be dewatered is guided such that the sealing element sits optimally against the jacket and a good sealing effect is achieved.
2. Discussion of Background Information
There is disclosed in U.S. Pat. No. 5,580,424 a sealing element arranged in a holder and clamped to the holder, such a sealing element having a separate piston that is pressed against the sealing element by means of a spring. The spring is designed in such a way that a movement of the sealing element in the direction of a roll jacket is not prevented, but the sealing element is held when the pressure in an application pressure tube is eliminated.
In a device as disclosed in German Patent DE-AS 1 135 745, legs of a sealing strip are respectively arranged in a space between walls of a guide for the sealing strips, with the thickness of the respective legs being somewhat less than the width of the space between the walls. To reduce the penetration of air, a small pneumatic seal in the form of a rubber tube, which is connected to a pressurized air source and sits against the sealing strips in order to provide a seal, is provided between each sealing strip and the exterior walls of the guide.
Forming grooves for a sealing strip in the lateral walls of a holder and placing sealing tubes in those grooves that can unroll in the groove in the application pressure direction is known from U.S. Pat. No. 2,649,719. The sealing strip can move freely due to the unrolling tubes inside the slit formed by the lateral walls of the holder.
In a device as disclosed in German Patent DE-AS 1 146 350, sealing strips that can be pressed against the inner surface of a roll jacket are loosely guided in the body of a suction chamber and supported inside the suction chamber by pressure chambers and outside by ribs.
The invention resides in a sealing device and a process of the type described above that will provide uniformly good sealing of the pressure zone during operation in the simplest possible manner while avoiding application of excessive pressure.
This is achieved by having the receptacle area designed as a clamping receptacle and the sealing element being acted upon by a clamping force through clamping surfaces of the clamping receptacle.
This produces a frictionally-engaged connection between the holder and the sealing element which can hold the sealing element securely in the respective position in relation to the moving surface while simultaneously ensuring a seal between the holder and the sealing element.
Moreover, this allows the clamping force to be applied in such a way that the sealing element initially sits against the moving surface with an application force sufficient to overcome the clamping force and the application pressure can subsequently be reduced, whereupon the sealing element is held in its set sealing position by the clamping force exercised on the sealing element by the holder through its clamping surfaces.
According to an embodiment of the invention, at least one clamping surface is partially formed by a clamping body.
Such clamping body can be deliberately adjusted to the respective conditions of use. For example, if vibrations of the moving surface, particularly a rotating jacket of a suction roll or a ventilation roll, are anticipated which will affect the position of the sealing element, the clamping body that will contribute to the frictionally-engaged connection between the holder and the sealing element may be elastically ductile so that the vibrations transferred to the sealing element can be absorbed. The occurrence of a so-called xe2x80x9cslip-stickxe2x80x9d effect can be effectively prevented in this manner, so that the sealing element remains in its set position in relation to the roll jacket, in spite of the vibrations. An excess application pressure or surface pressure between the sealing element and the roll jacket is thus avoided, thereby reducing wear on the sealing element.
In contrast, the clamping body may be made of a less elastic material if no disruptive vibrations are expected and if the xe2x80x9cslip-stickxe2x80x9d effect, which is specifically desirable in the case of suction rolls with poor concentricity, is to be promoted.
According to the invention, a sealing device for laterally sealing at least one excess pressure or vacuum zone adjoins a moving surface in a paper-making machine, the sealing device comprising a holder, a receptacle area in the holder and at least one sealing element in the receptacle area. The sealing element is movable relative to the holder for placement against the moving surface. The receptacle area is designed as a clamping receptacle having clamping surfaces thereon. The sealing element is acted upon with a clamping force through the clamping surfaces of the clamping receptacle.
The sealing element substantially completely fills the receptacle area in at least one plane perpendicular to the direction of movement of the sealing element. The receptacle area is designed as a receptacle channel open to the moving surface, which channel has one of, a square or rectangular inner cross-sectional area, and the lateral surfaces delimiting the receptacle channel are designed as clamping surfaces. At least one clamping surface is partially formed by a clamping body, arranged in a groove that is formed in a lateral wall of the holder and is open to the sealing element.
In one embodiment of the invention, the clamping body comprises a seal element which is elastically ductile.
According to another embodiment of the invention, the clamping body includes a clamping pressure tube arranged between the sealing element and a lateral wall delimiting the receptacle area.
The sealing element is placed against the moving surface by way of at least one application pressure tube arranged between the sealing element and a delimiting surface of the receptacle area facing away from the moving surface. The pressures present in the application pressure tube and in the clamping pressure tube are at about the same level at least during placement or application of the sealing element against the moving surface. The application pressure tube and the clamping pressure tube are connected to a joint pressure circuit. The clamping pressure tube is arranged in a groove formed in the surface of the lateral wall.
According to another aspect of the invention, a piston is movable in the groove and arranged between the clamping pressure tube and the sealing element. The piston is made of a material having a low degree of elasticity.
According to the invention, the sealing element includes a wear section cooperating with the moving surface and a clamping section cooperating with the holder, wherein the wear section and the clamping section are made of two different materials. The holder is movable relative to the moving surface with a component that is parallel to the direction of placement. The holder is movably mounted, particularly spring mounted on one of, a suction or ventilation box.
The sealing device is used for laterally sealing at least one pressure zone adjoining the interior or exterior wall of a rotating jacket of one of, a suction roll, or a ventilation roll, or a moving belt. The device may be mounted between one of, a suction or ventilation box and a rotating jacket of one of, a suction roll, or a ventilation roll, or a moving belt.
The sealing element is designed as a sealing strip extending at least substantially over the entire roll length. The sealing element is acted upon by a clamping force through clamping surfaces of the holder. At least one clamping surface is formed at least partially by a clamping body arranged in a channel formed in a lateral wall of the holder and open to the sealing element, and that includes a clamping pressure tube arranged between the sealing element and a lateral wall delimiting the receptacle area. The sealing element can be placed against the moving surface by way of at least one application pressure tube, arranged between the sealing element and a delimiting surface of the receptacle area facing away from the moving surface. The pressures present in the application pressure tube and in the clamping pressure tube are at about the same level at least during placement or application of the sealing element against the moving surface. The application pressure tube and the clamping pressure tube are connected to a joint pressure circuit.
According to the invention, the sealing device is used for laterally sealing at least one of, excess pressure zone or vacuum zone adjoining a moving surface in a paper-making machine. The sealing device comprises a holder, lateral walls defined in said holder and at least one sealing element positioned inside said holder and movable relative thereto for placement against the moving surface. The sealing element has lateral walls in sliding contact and frictional engagement with the lateral walls on the holder. A clamping force is exerted by the lateral walls in said holder on the lateral walls of the sealing element to inhibit movement of the sealing element away from the moving surface.
The sealing device further comprises a groove formed in at least one of the lateral walls of the holder, the groove being open to the sealing element. A clamping body is arranged in the groove for inhibiting movement of the sealing element relative to the holder. The width of the seal element exceeds the width of the holder by about 0.05 mm, and preferably by about 0.1 mm.
The clamping body comprises a clamping pressure tube located in the groove and a piston arranged between the sealing element and the clamping pressure tube. The piston is made of a material selected from among rubber or plastic, such as polytetrafluoroethylene. The sealing element wear section is made of a material having good lubricating properties, such as a plastic material with high content graphite.
The holder is made of a different material than the clamping section. The material selected could be a mettalic material, e.g., special steel, brass, or bronze.
At least one application pressure tube is provided for moving the sealing element against the moving surface, the application pressure tube being arranged in the groove between the sealing element and a delimiting surface of the groove facing away from the moving surface.
A fluid pressure circuit supplies to the application pressure tube and to the clamping pressure tube about the same pressure level at least during application of the sealing element against the moving surface. The fluid pressure circuit comprises a common pressure circuit for the application pressure tube and the clamping pressure tube.
The sealing element comprises a wear section cooperating with the moving surface and a clamping section cooperating with the holder, the wear section and the clamping section being made of two different materials.
The holder is movable relative to the moving surface in a direction parallel to the direction of movement of the seal element. Additionally, the holder is spring mounted on one of, a suction or a ventilation box.
A chamber disposed between the bottom of the holder and the suction box. The chamber is open to ambient and further comprises a first seal disposed between the holder and the suction box. Alternatively, the chamber is open to the suction box and further comprises a second seal disposed between the holder and the suction box.
The sealing element comprises a wear section cooperating with the moving surface and a clamping section cooperating with the holder, the wear section being provided with a slope on one side thereof.
The invention contemplates a paper-making machine comprising a moving surface. An excess pressure zone or vacuum zone adjoins the moving surface. A sealing device for laterally sealing the zone comprises a holder, at least one sealing element positioned inside the holder and movable relative thereto for placement against the moving surface. The sealing element has lateral walls in sliding contact and frictional engagement with the lateral walls on the holder. A clamping force is exerted by the lateral walls in the holder on the lateral walls of the sealing element to inhibit movement of the sealing element away from the moving surface. A clamping body inhibits movement of the sealing element relative to the holder. The clamping body comprises a clamping pressure tube and a piston arranged between the sealing element and the clamping pressure tube. At least one application pressure tube moves the sealing element against the moving surface. A fluid pressure circuit supplies pressure to the application pressure tube and to the clamping pressure tube.
The invention is also attained by way of a process for applying a clamping force, through clamping surfaces of a clamping receptacle during its movement relative to the holder and in its applied state, on a sealing element in the clamping receptacle.
The process for laterally sealing at least one excess pressure or vacuum zone adjoining a moving surface in a paper-making machine by way of a sealing device that includes at least one sealing element, comprises arranging the sealing device in a receptacle area of a holder and placing the sealing device relative to the holder against the moving surface. The receptacle area is designed as a clamping receptacle. The process further comprises acting on the sealing element with a clamping force through clamping surfaces of the clamping receptacle during its movement relative to the holder and in its applied state.
Additionally, the process further comprises clamping the sealing element with a clamping force that is at least substantially constant over time. Further, the process comprises varying the clamping force as a function of at least one of, the distance of the sealing element from the moving surface or as a function of an application force that acts upon the sealing element for placement onto the moving surface.
The process further entails setting an application force as a function of the ratio between the clamping force and a bending force necessary for adjustment of the sealing element to the contour of the moving surface, once the sealing element has been placed against the moving surface. Additionally, the process entails reducing the application force, once the sealing element has been placed against the moving surface.
The process further comprises selecting the clamping force to be greater than a bending force and reducing the application force to approximately zero, once the sealing element has been placed against the contour of the moving surface.
According to another aspect of the invention, the process comprises selecting the clamping force to be less than a bending force and reducing the application force to approximately the difference between the bending force and the clamping force, once the sealing element has been placed against the contour of the moving surface.
Preferred embodiments of both the sealing device according to the invention and the sealing process according to the invention are further described in relation to the description and the drawings.
Other exemplary embodiments and advantages of the present invention may be ascertained by reviewing the present disclosure and the accompanying drawing.